System for amplifying feeble electric currents.



L. DE FOREST.

SYSTEM FOR AMPLIPYING PEBBLE ELECTRIC OURRENTS.

" APPLICATION FILED JUNE 20, 1907.

995,126, Patented June13, 1911.

UNITED STATES PATENT OFFICE.

LEE on FOREST, OF NEw YORK, N. Y., ASSIGNOB 'ro DE FOREST RADIO A CORPORATIQN OF NEW YORK.

TELEPHONE 00.,

SYSTEM FOR AMILIFYING FEEBLE ELECTRIC CURRENTS.

Specification of Letters Patent. Patented J 11116 13, 1911.

Application filed June 20, 1907. Serial No. 379,924.

To all whom it may concern: Be it known that I, LEE DE FOREST, a

. citizen ofvthe United States, and a resident phone transmit/3?,

of New York, in the county of New York and State of New York, have invented a new and useful Improvement in Systems for Amplifying Fe eble Electric Currents, of which the following is a specification.

The present invention relates to systems for amplifying feeble electric currents and itsobject is to provide such system capable of use in wire telephone or telegraph "lines and in space telegraph or space telephone systems.

My invention consists essentially in the interposition between the currents to be ainplified and the signal indicating device of a source of high frequency electrical oscillations, hereinafter more fully described, and between said source of electrical oscillations and said signal indicating device I may interpose a circuit including an oscillation responsive device. I

The drawings which accompany and form a part of this specification illustrate conventionally several arrangements of apparatus and circuits whereby the above mentioned object has been realized in practice; but it will be understood that I do not limit myself to the precise arrangements shown inasmuch as many modifications may be made therein without departing from the principle of my invention.

In the drawings, Figure 1 represents one form of my invention applied to a wire telephone system. Fig. 2 is a diagram representing the present invention applied to a :pace telegraph or telephone receiving sysem. a

In the figures, D is a source of direct current, R. is a resistance, inductive or noninductive, L represents an inductance which may be employed, C C 0 C C are condensers, M M M M, are transformers, B B B B" are batteries, K is a micro- N is a megaphone, and T is a signalicating device which may be a telephone receiver.

In Fig. 1, the circuit S 0 M and in Fig. 2 the circuit S C M represents a source of high frequency electrical oscillations having a spark frequency higher than the more essential frequencies accompanying speech waves and preferably higher than the limit ofaudibility, and as shown in the present instance said circuit is shown as a singingarc circuit capable of developing practi cally continuous electrical oscillations when it is connected with the source of direct current D through leads of high resistance or high inductance.

In Figs. 1 and 2 I have represented the discharger for the condenser C as consisting of two electrodes J J sealed in a receptacle A and maintained in any suitable atmosphere under small or large pressure. The filament F may be heated-by the current of the battery B. It will be unde'rstood however that I do notlimit myself to any special type of discharger and that any suitable source of high frequency oscillations having the characteristics above set forth may be substituted for the circuit S C M or S C M.

0 represents an oscillation detector of any suitable type and herein shown as an audion consisting of the evacuated vessel A having sealed therein the filament F heated by the battery B, the grid- G and the plate H,

the latter being connected'to the positive pole of the battery B and with the signal indicating des-ice T. The audion O is associated in any suitable manner with the tuned circuit M 0 G which in turn is associated with the source 'of high frequency oscillations. In the present instance said tuned circuit is shown as inductively related to the circuit S C M by means of the oscillation transformer M, although any other associating means may be employed.

In Fig. 2 V represents a receiving antenna connected to earth E through the primary I of the oscillation transformer M whose secondary I forms part of the tuned receiving circuit which includes the condensers C 0 Associated with said tuned receiving circuit in any suitable manner is the audion or other suitable oscillation detector 0, the local circuit of which includes the primary of the transformer M'fand if desired, the choke-coils L L.

The telephone circuit and the local cirwhich carries the currents to be amplified with said oscillation circuit, and furtherof the turned circuits M C O with the oscillation circuit should be maintained by a transformer of small magnetic leakage, if a transformer is employed.

In Fig. 2, U represents a metallic case which may be grounded at E E.

The operation is as follows The feeble electrical currents developed in the primary of the transformer M of the transformer M or M are impressed upon the high frequency oscillation circuit, thereby Varying the amplitude of the oscillations in said circuit in accordance with the sounds initiating said feeble currents. The' energy of said oscillations, so varied in amplitude, is translated to the circuit M C C attuned to the frequency of said oscillations, and actuates the oscillation responsive device 0 causing thereby currents in the circuit of the telephone T closely approximating in form those developed in the primary or M but greatly exceeding the latter in amplitude. It has been found that the tuned receiving circuit M C C need not be employed and also that the oscillation detector 0 may be omitted as shown in Fig. 3. In this case the telephone receiver T responds .to variations. in the amplitude of the currents developed in the line Q Q, the frequency of said currents exceeding that to which the diaphragm of said telephone responds.

I claim:

1. The combination with a circuit carrying feeble electric currents of a source of practically-continuous electrical oscillations associated with said circuit, and including arc electrodes, with capacity and inductance in series shunt thereto, an oscillation responsive device, a circuit attuned to the frequency of said electrical oscillations interposed between said source and'said oscillation responsive device, and a local circuit including therein a signal indicating device and a source of electro-motive force, associated with said oscillation responsive device.

2. The combination with a circuit carrying feeble electric currents of a source of practically-continuous electrical oscillations associated with said circuit and including arc electrodes with capacity and inductance in series shunt thereto, an oscillation responsive device, a circuit attuned to the frequency of said electrical oscillations interposed between said source and said oscillation responsive device, a local circuit including therein a signal indicating device associated with said oscillation responsive device, and a source of electromotive force in circuit with said signal indicating device.

3. The combination with a circuit carrying feeble-electric currents of a'source of practically-continuous electrical oscillations associated with said circuit, said source comprising a singing-arc circuit provided with inclosed arc-electrodes, an audion associated with said singing-arc circuit, and a local circuit including a telephone receiver and a source of electromotive force associated with said au dion.

4. The combination with a circuit carrying feeble electric currents of a source of' high frequency electrical oscillations having a frequency higher than the more essential frequencies accompanying speech Waves, an oscillation responsive device associated with said source of electrical oscillations and a signal-indicating device associated with said oscillation responsive device.

In testimony whereof, I have hereunto subscribed my name this 17th day of June 1907 LEE DE FOREST.-

Witnesses:

THOMAS I. GALLAGHER, Roscon KENT. 

